Influence of Thymectomy,Splenectomy,and Cortisone on Carcinogenesis

Abstract

Groups of outbred albino CTM mice were either thymectomized or splenectomized at 4 weeks of age and administered urethan 0.4 percent in the drinking water for 10 days at 5 weeks. In comparison with intact, urethan-treated animals, the thymectomized, urethan-treated mice had a slightly lower incidence of malignant lymphomas (19 against 24 %), a marked decrease of mammary tumors (31 against 62%), and increased incidence of lung adenomas (84 against 48%) and of skin papillomas (10 against 1%). Thymectomized, but otherwise untreated mice developed less lymphomas and mammary tumors than intact, untreated controls. Splenectomy did not modify significantly the tumor incidence. In a second experiment, groups of CTM mice were administered either 1 mg of cortisone s. c. daily for 10 days or urethan in the drinking water for 5 days followed by 5 days of cortisone or viceversa, or urethan alone. No major differences in the tumor incidence in the various groups were observed, but for a decreased incidence of thymic lymphosarcomas in the group with cortisone after urethan. In a third experiment, CTM mice were given 2 mg urethan within the first day after birth and thymectomized or sham operated during the anesthesia caused by the urethan. Both groups had a very high incidence of hepatomas and lung adenomas, and developed only few lymphomas and mammary tumors. Finally, a group of C3H mice thymectomized at birth under Nembutal anesthesia, developed a considerably lower incidence of hepatomas and mammary tumors than sham operated animals.